The previous page, 'Hook comparison', shows a table which bears the simplified result of many hook measurements and much work in ascertaining sensible range limits for size and other hook characteristics. This page and the next will show all the detail.
Several points need to be understood:
One often comes across the expressions 'short shank' and 'wide gape'. I have even seen a hook described as both. The latter of the two is a nonsense phrase. If the gape is the only element which commonly defines the hook size then there can be no such thing as 'wide gape' A "Size 14 wide gape" is actually a size 12 short shank (or possibly 13).
It is important to realise that hook size does not define fly size. The latter is dependent on the length of the shank - which is independent of the hook size. This makes it important for the description of a hook to be unambiguous as regards the shank relative to the gape. I find that the most meaningful description is a statement of the actual ratio of shank/gape.
The shank is traditionally defined as the length from the neck of the eye to the bend. I find this to be impossible since the start of the bend can almost never be pinpointed with any certainty. Far more relevant is the 'shank overhang', i.e. the length of the shank which protrudes forward from the point directly adjacent to the point of the hook. Diagram follows
This is the system I have used for all recorded measurements and shank/gape ratios are according to this system.